A Photos library appears as one package in Finder but contains a managed database, originals, edits, previews, and metadata.
Do not delete internal package files based on a size or duplicate result. Use the Photos app to delete assets, merge supported duplicates, export originals, or optimize Mac storage.
Before moving a library, quit Photos, back it up, and follow Apple’s supported process. Keep external storage mounted and formatted appropriately.
Similar-looking photos can represent edits, Live Photo resources, bursts, or intentional variants.
Use diCleaner on exported normal image folders when you want direct file-level review.